2-plastic parts design guideline

ShanghaiYanfengJohnsonControlTechnicalCenter1PlasticPartDesignGuidelinesSpecificforAutomotiveComponentsInjectionMoldingTechnicalCenterShanghaiYanfengJohnsonControlTechnicalCenter2TableofContentsIntroduction:BasicConsiderations1)NominalWall2)Ribs3)Undercuts4)Holes5)Bosses6)Flanges7)PartingLine8)Gating9)LivingHingeChapter10)Weld/Meld/KnitLines11)Graining12)Thick/ThinTransitions13)BasicToolingConsiderations14)Design/ToolingAidesShanghaiYanfengJohnsonControlTechnicalCenter3BasicConsiderations:Considered:FunctionalandManufacturableAlltheguidelinesareeffectedbythefollowingthreegeneralareas:1.Partapplication2.Process1.MaterialShanghaiYanfengJohnsonControlTechnicalCenter4PartapplicationTwoprimarycategories–non-structural(decorativetrim)•moreconcernedontheaestheticsoftheclass'A'surface.•Examples:sideshields,seatbacks(exposed),doortrim,A/B/Cpillartrim,andI/P(instrumentpanels)–structuralparts(outofviewoftheconsumer)Examples:I/Psubstrate,structuralbolsters,andflipperpanels(covered)ShanghaiYanfengJohnsonControlTechnicalCenter5ProcessInjectionandBlowmolding–Blowmoldingislimitedtoactionsinthetoolthatwouldbeusedtocreatesideholesorundercutfeaturesthatcanbedoneininjectionmolding.–Injectionmoldingisgenerallyrestrictive(notincludingspecialprocesses)inthecross-sectionalsizeofthepartShanghaiYanfengJohnsonControlTechnicalCenter6MaterialMaterialusedwillalsoeffecttheguidelinesandconsultationwiththematerialsupplierisveryuseful.Highlyfilledmaterialswillallowvariationsinsomerulesaswillunfilledinothers.Generally,whenamaterialischosenforanapplication,costandpropertiesarethetwomajorfactorsthatwillbeusedtodecide.ShanghaiYanfengJohnsonControlTechnicalCenter71:NominalWall1.1Importance:veryimportantinprocessingandfunctionShanghaiYanfengJohnsonControlTechnicalCenter8surfacedefects;trappedgas,voids,orpressuredropvariationsthatmakeprocessingdifficultsurfacedefects,trappsurfacedefects,trappedgas,voids,orpressuredropvariationsthatmakeprocessingdifficult.decorativetrimcomponentsis2.5mmAveragenominalwallthicknessstructuralcomponentsare3.0mm1.3Strength1.2Flow/Filling:Consistentnominalwall-------BetterVariedthicknessesofthenominalwall--AvoidFlowofplasticwillbethroughthethickersectionsfirstShanghaiYanfengJohnsonControlTechnicalCenter91.3StrengthProper'packing'ofthepartismoredifficultifthenominalwallisvarying.Thiscouldleavevoidsorhigherstressesinsectionsofthepartthatcouldeffecttheperformance.1.4WarpageDifferentnominalwallthicknesswillhavedifferentcoolingratesanddifferentdegreesoforientationofpolymerchains.Thiscancauseexcessivewarpagewhenpartcomesoutofthetool.ShanghaiYanfengJohnsonControlTechnicalCenter101.5ProcessingProcessingofplasticcomponentsarebasedoncoolingtimeinthemold.Thethickerthewallthelongerittakestocooltoapointwerethepartcanbeejectedortakenoutofthemold.Ifaparthasvaryingwallthickness,thecycletimewillbebasedonthethickersection.Aconsistentnominalwallisbetterforcontrollingthecycletimeandcostsoftheparts.1.6ExceptionsSometimesthedesignrequiresthickersections(i.e.aheavybossisrequiredandthenominalwallneedstobethickertopreventasink),butyoudonotwanttomakethewholepartthickerandwastematerialortime.Transitionfromathickertothinsectionshouldbeutilized.Ifthethickersectionisreallyexcessive,are-evaluationofthedesigniswarranted.ShanghaiYanfengJohnsonControlTechnicalCenter112:Ribs2.1Uses:StiffnesstoapartStrengthtoapart3)Stabilitytoapart(warpage)4)Methodofattachment5)Methodofpositioningpartinassembly*bothappearanceandfunctionalityShanghaiYanfengJohnsonControlTechnicalCenter12Improperribs:warpageduetonon-uniformshrinkageRibsareDifficult-ToFill-ToVent-ToEject2.2NominalwallratioAvoidsinkmarks---Generalruleofthumb:50%Materialdependent:somematerialsallowagreaterorlesserratioFilledmaterials:largerribs(Ifthepartisstructuralandhidden,thewalltoribratiocanbemore.)ShanghaiYanfengJohnsonControlTechnicalCenter132.3DirectionalBecarefulwhendeterminingribdirectioninthepart.Ifribsare90degreestomaterialflow,partmayexhibitablushorhighlightovertopofribs.Todiminishchanceofribreadout,ribsshouldbedesignednearedgesofpartwherepossible.ShanghaiYanfengJohnsonControlTechnicalCenter142.4DraftandDepth-draftanglesof1-1.5degreesaverage(notlessthan0.5degrees)-Thedeepertherib-thethinneritwillbeattheend-harderitwillbetofillAverageriblengthisgenerally2.5-3.0xwallthicknessShanghaiYanfengJohnsonControlTechnicalCenter152.5JoinRadiusToavoidstresscracks,aradiusshouldbeappliedtothejoinareaoftheribbaseandnominalwall.Thelargerthebetter,however,keepinmindthatthejoinradiuswilladdmaterialandincreasethewalltoribratio.Generallya0.25mmjoinradiusshouldbeenough,youjustwanttobreakthesharpedges.ShanghaiYanfengJohnsonControlTechnicalCenter162.6ToolingConsiderations-Ribsareusuallyburnedintothetool.Thisleavesaroughfinishthatneedstobebenchedorsmoothedout.Thedeepertheribs,themoredifficultitisforthetoolertobenchthepart.-PlacementofribinpartDiedirection(directiontoolopensandcloses)oralonganedgeIftheribsarenotindiedirection,theywillrequireaslideorlifteraddedtothetool.Thiswilladdcostandtimingtoatool.ShanghaiYanfengJ